Atrial fibrillation is one of the most common cardiac arrhythmia. Health consequences associated with atrial fibrillation include decreased cardiac output, less regular ventricular rhythm, the formation of blood clots in the atria! appendages, and an increased incidence of stroke. While some drugs are available for the treatment of atrial fibrillation, they have a number of side effects which reduce their therapeutic utility.
Unlike patients afflicted with ventricular fibrillation, patients afflicted with atrial fibrillation are conscious. The pain associated with the administration of the defibrillation shock can be severe, and there is a need for means of carrying out atrial defibrillation in a manner that is less painful to the patient being treated.
U.S. Pat. No. 5,165,403 to R. Mehra discloses an implantable lead system useful for defibrillating (or "cardioverting") the atria of a patient's heart. In the disclosed system, one electrode is positioned in either the great cardiac vein or coronary sinus of the heart, and another electrode is positioned in either the right atrium or superior vena cava of the heart. Configurations for reducing the pain associated with defibrillation are not disclosed.
U.S. Pat. No. 5,209,229 to Gilli discloses an implantable atrial defibrillation device employing multiple implantable electrodes. Upon detection of atrial fibrillation, a first electrode configuration is selected and a defibrillation shock administered. If atrial fibrillation remains after that shock, then a second electrode configuration is selected and a second defibrillation shock administered. Multiple defibrillation pulse dministrations are only used when the initial defibrillation pulse fails, and not as a means to reduce pain associated with atrial defibrillation.
In view of the foregoing, an object of the present invention is to provide methods and apparatus for carrying out atrial defibrillation that will reduce the pain associated therewith.
A further object of the present invention is to provide methods and apparatus for carrying out atrial defibrillation that will reliably treat atrial fibrillation.
A still further object of the present invention is to provide methods and apparatus for treating atrial fibrillation that minimizes the extent of the surgical intervention involved in implanting the necessary defibrillation electrodes, and minimizes the complexity involved in implanting the necessary defibrillation electrodes.